1. Field of Invention
The invention relates to a process for the production of hydraulic binders, crude steel and/or alloys, such as, e.g., FeCr or FeV, from basic steel slags containing chromium and/or vanadium.
2. Description of Related Art
For producing cement clinker and special binder qualities having high .alpha.-belite contents and high ultimate strengths from metallurgical slags it has already been proposed to mix together liquid slags from reduction processes and from steelworks processes and, if required, add lime thereto. When mixing acid liquid slags as they incur, for instance, in blast furnace processes and basic steelworks slags as they incur, for instance, in the form of converter slags, heat is released since this is an exothermic neutralization reaction.
As a rule, a relatively high portion of blast furnace slag has been required for the production of hydraulic binders. Besides classical portland cement, such blast furnace slags have gained great importance as slag cements. Slag cements in the narrower sense are finely ground mixtures of gypsum, clinker and blast furnace slag, a slight amount of gypsum usually having been added for controlling the setting time, as is the case with portland cement.
The usability of basic slags as they incur from steelworks processes, for instance as LD slags, in most cases is substantially limited. The disposal of electric arc furnace slags, like that of steel slags, involves relatively high expenditures. At present, steelworks slags and electric arc furnace slags are, for instance, recycled into the blast furnace, the remainder being used in road construction or dumped. However, due to increasing scrap charge quotas, the contents of heavy metals and, in particular, the contents of chromium and vanadium in steel slags and electric arc furnace slags has constantly increased such that simple dumping no longer appears admissible with the concentration of such heavy metals rising. In the future, such slags presumably will have to be dumped on dumping grounds for special waste, the operation of which involves considerable costs.
Steel slag stands out for its relatively high iron oxide content brought about by the refining process. Usual steel slag contains manganese oxide and iron oxide to an extent that may amount up to 33 wt. %. Blast furnace slag stands out for its relatively favorable hydraulic properties. Morever, blast furnace slag has a substantially lower iron oxide content, its processing to basic construction material thus being considerably facilitated.
Binder additives influencing the setting time, the fatigue strength and other parameters essential to binders have gained more and more importance in the production of hydraulic binders. Such additives may be used in connection with conventional hydraulic binders, such as, for instance, slag cement or portland cement, for adjusting the desired properties.